The present invention relates to welding and, more particularly, relates to welding the abutting ends of tubular members.
Conventionally, tubular members, such as hydraulic piping and end fittings for piping, are welded together by forming a weld joint along a circumferential path defined by the interface of the abutting ends of the coaxially aligned members. For example, in the aerospace industry, piping and end fittings are typically welded together through a process known as gas tungsten-arc welding (xe2x80x9cGTAWxe2x80x9d), although other welding processes may be used depending on the material used to form the tubular members. During the GTAW process, an arc is established between the tubular members and a nonconsumable tungsten electrode positioned adjacent the interface of the abutting ends of the tubular members. The weld area is shielded with an inert gas, such as argon, helium or a mixture of these gases, prior to, during and after welding. The GTAW process is used for a variety of metals, including aluminum, magnesium, titanium, stainless steel, and refractory metals, and produces high quality weld joints with good surface finish.
When welding tubular members using the GTAW process, an orbital welding device is typically used to move the electrode along the circumferential path defined by the interface of the abutting ends of the coaxially aligned tubular members. One example of an orbital welding device is disclosed in U.S. Pat. No. 4,810,848 to Kazlauskas, which discloses a portable tube welder having a gear driven spur gear rotatably mounted within a housing. Openings are provided on opposite sides of the housing to receive the abutting ends of the tubes. Similarly, the spur gear defines an opening, which is coaxially aligned with the openings in the sides of the housing, to receive the abutting ends of the tubes. An electrode is mounted on the spur gear such that as the spur gear is rotated, the electrode moves along a circumferential path defined by the interface of the abutting ends of the tubes to form a weld joint. Prior to welding, the abutting ends of the tubes are secured in place within the opening defined by the spur gear using clamshell-type clamps mounted to the corresponding sides of the housing. Each clamp includes two hinged clamping plates with an over-center locking mechanism to latch the clamping plates around the tubes.
However, the clamshell-type clamps disclosed in the ""848 patent are not particularly suited for high volume usage, since securing the abutting ends of the tubes in place within the opening defined by the spur gear can be both labor and time intensive. In addition, to facilitate mobility, the housing of portable tube welders, such as the welder disclosed in the ""848 patent, are typically designed to provide only minimal support to the clamshell-type clamps and, thus, high volume usage can lead to bending or warping of the portions of the clamps that contact the tubes, as well as the housing. Damage to the portions of the clamps that contact the tubes and/or the housing can result in misalignment of the tubes inside the spur gear, which in turn can lead to defective weld joints. In addition, while clamshell-type clamps may provide adequate support for short, small diameter tubes, such clamps typically do not provide adequate support for long and/or large diameter tubes, such as those used during the fabrication of commercial and military airplanes and the like.
Thus, there is a need for an improved orbital welding device for forming weld joints about the ends of abutting tubular members. The welding device should be capable of effectively supporting the tubular members during welding and allow for the efficient insertion and removal of the tubular members before and after welding. Additionally, the welding device should be easily adaptable to varying tube geometries and sizes.
The present invention provides an apparatus for forming a weld joint between abutting ends of first and second tubular members. The welding apparatus includes a housing having first and second sides defining an interior therebetween. The first side of the housing defines an aperture adapted to at least partially receive the abutting end of the first tubular member. The second side of the housing defines an aperture coaxially aligned with the aperture defined by the first side and adapted to at least partially receive the abutting end of the second tubular member. According to one embodiment, the housing comprises a base plate to support the housing. According to another embodiment, the interior of the housing is water-cooled.
The welding apparatus includes a welding electrode movably mounted to the interior of the housing and projecting toward the abutting ends of the first and second tubular members to thereby define an arc gap between the electrode and the abutting ends. According to one embodiment, the welding electrode comprises a nonconsumable tungsten electrode. According to another embodiment, the housing includes a hinged portion between the first and second sides of the housing for observing the positioning of the abutting ends of the first and second tubular members relative to the welding electrode. The welding apparatus includes an electrical source for supplying welding energy to the welding electrode and a pressurized-gas source for supplying inert gas to the arc gap. The inert gas may include argon, helium or a mixture of these gases.
The welding apparatus includes a chuck assembly secured to the first side of the housing. According to one embodiment, the chuck assembly includes a plurality of slidable chuck jaws each having first and second ends. The first end of each chuck jaw defines a gripping surface for frictionally engaging at least a portion of the surface of the first tubular member such that the abutting end of the first tubular member is secured within the interior of the housing adjacent the welding electrode. The chuck assembly includes means, in operable communication with the chuck jaws, for moving the chuck jaws to thereby urge at least a portion of each of the gripping surfaces into frictional engagement with the surface of the first tubular member. According to another embodiment, the first ends of the chuck jaws include replaceable inserts to accommodate different diameter tubular members. According to another embodiment, the chuck jaws are electrically grounded to the housing.
According to still another embodiment, the chuck assembly includes a plurality of slidable chuck jaws each having first and second ends and first and second sides. The first end of each chuck jaw defines a gripping surface for frictionally engaging at least a portion of the surface of the first tubular member. The first side of each chuck jaw includes a pin protruding therefrom. The chuck assembly, according to this embodiment, also includes a rotatable plate defining a plurality of arcuate slots each adapted to receive the pin protruding from the first side of one of the chuck jaws. Advantageously, rotation of the plate moves the pin radially along a path defined by the arcuate slot to thereby urge at least a portion of each of the gripping surfaces into frictional engagement with the surface of the first tubular member to thereby secure the abutting end of the first tubular member within the interior of the housing adjacent the welding electrode.
The welding apparatus also includes a support tool for supporting the second tubular member. The support tool is attached to the second side of the housing opposite the chuck jaws such that the abutting end of the second tubular member is secured within the interior of the housing adjacent the welding electrode and the abutting end of the first tubular member. According to one embodiment, the support tool is slidably attached to the second side of the housing opposite the chuck jaws such that the support tool is movable relative to the second side of the housing to position the abutting end of the second tubular member within the interior of the housing adjacent the welding electrode and the abutting end of the first tubular member. According to another embodiment, the support tool includes a plurality of support shafts slidably mounted to the second side of the housing such that the support tool is movable relative to the second side of the housing. The support tool may comprise a chuck assembly or a collet.
According to one embodiment, the welding apparatus includes means, in operable communication with the welding electrode, for moving the electrode circumferentially about the abutting ends of the first and second tubular members to thereby form the weld joint. The moving means may include a drive assembly and a motor in operable communication with the drive assembly. The drive assembly may include a belt drive, a gear drive or a combination of both. According to one embodiment, the drive assembly includes a slip clutch. According to another embodiment, the welding apparatus includes computing means in electrical communication with the motor. According to another embodiment, the motor includes a tachometer and the computing means includes an analog computer. According to still another embodiment, the motor includes a digital encoder and the computing means includes a digital computer.
According to another embodiment, the welding apparatus includes a motor in operable communication with the welding electrode such that the welding electrode is moved circumferentially about the abutting ends of the first and second tubular members to thereby form the weld joint. According to one embodiment, the motor includes a drive assembly, wherein the drive assembly may include a belt drive, a gear drive or a combination of both. According to another embodiment, the drive assembly includes a slip clutch. According to another embodiment, the welding apparatus includes a computing means in electrical communication with the motor. According to another embodiment, the motor includes a tachometer and the computing means includes an analog computer. According to still another embodiment, the motor includes a digital encoder and the computing means includes a digital computer.
The present invention also provides a method of welding the abutting ends of first and second tubular members, including the steps of inserting the abutting end of the first tubular member into an aperture defined by a first side of a housing, the housing having a welding electrode movably mounted therein and projecting toward the abutting end of the first tubular member to thereby define an arc gap between the welding electrode and the abutting end of the first tubular member. A plurality of slidable chuck jaws are moved into frictional engagement with at least a portion of the surface of the first tubular member such that the abutting end of the first tubular member is secured within the aperture defined by the housing adjacent the welding electrode. A second tubular member is attached to a support tool. The abutting end of the second tubular member is inserted into an aperture defined by a second side of the housing such that the abutting end of the second tubular member is adjacent the welding electrode and the abutting end of the first tubular member. According to one embodiment, the inserting step includes moving the support tool toward the aperture defined by the second side of the housing. Inert gas is injected into the arc gap to shield the weld area from contaminants. According to another embodiment, the step of inserting a first tubular member follows the step of inserting a second tubular member. An arc is formed between the welding electrode and the abutting ends of the first and second tubular members. The welding electrode is moved in a circumferential path about the abutting ends of the first and second tubular members to thereby form a weld joint. According to one embodiment, the method may include the steps of measuring the angular velocity of the motor and then automatically adjusting the angular velocity of the motor to thereby modify the position of the welding electrode about the abutting ends of the first and second tubular members. After the abutting ends of the first and second tubular members have been welded together the plurality of slidable chuck jaws are moved out of frictional engagement with the surface of the first tubular member. The welded assembly can then be removed through the aperture defined by the first side of the housing.
Accordingly, there has been provided an orbital welding device and associated method of manufacture for forming weld joints about the ends of abutting tubular members. The welding device is capable of effectively supporting the tubular members during welding and allows for the efficient insertion and removal of the tubular members before and after welding. Additionally, the welding device is easily adaptable to varying tube geometries and sizes.